A connecting terminal block of the aforedescribed type may be used in any electrical apparatus or appliance, especially a heavy-duty electrical apparatus of appliance in which conductors of the apparatus are to be electrically connected to conductors connected to the main or electric supply line. In general, one contact of the terminal block can be considered to be a protective contact and can be connected to a grounding wire of the apparatus, a grounding wire of the supply source and either body or housing of the apparatus.
For that apparatus the terminal block can comprise an insulated body in which the connector contacts are arranged to make electrical connections between the various conductors of the supply source and the apparatus and which can include at least one protective contact which may also make an electrical connection with a wall of the apparatus upon which a terminal unit is mounted.
Of particular interest for the purposes of the invention is a terminal unit of the aforedescribed type in which the protective or grounding contact is a plug stamped from flat thin sheet metal and having two shanks which are received in a slot in the terminal body and are connected by a bight portion of the plug engageable in a window or slot in the wall of the housing or other structure of the apparatus to which the terminal block is to be affixed, e.g. by this plug.
The portion of the insulating body of the terminal provided with the slot in which the two-arm plug is received can thus be held against the wall of the apparatus provided with the window into which the plug fits and in which this plug is mechanically anchored.
The shanks or arms of the plug may form-fittingly and clampingly engage in recesses, cutouts or windows of the protective contact element within the body into which the grounding conductor of the supply source or the apparatus or both may be electrically connected.
The invention has as its basis the terminal block shown in FIG. 4 of German open application No. DE-OS 36 21 369 and the corresponding U.S. Pat. No. 4,728,295, issued Mar. 1, 1988 and commonly assigned with the present application. The two shanks which engage the contact element within the insulating body are here interconnected by a bridge piece which fits into the slot in the insulating body, while the plug portion has a U shape with a pair of arms lying wholly outside the body so as to be receivable in an appropriate slot or hole in the wall of the apparatus upon which the terminal block is to be mounted.
The two shanks rising from the bridge piece engage in openings in the protective contact element with the intention of providing an electrically effective contact therewith. The spring action is here formed between two arms of the U, wholly externally of the terminal body.
While this plug-type grounding connector has been found to be highly satisfactory in use, we have found that it is possible to improve upon the engagement of the grounding contact with the contact element within the terminal body, specifically by making that contact simpler and more effective for the purposes described.